The objective of this proposal is to evaluate the tendon repair process by means of a multidisciplinary approach. A variety of exercise conditions will be imposed in order to establish the conditions which will maximize the rate and strength of the repair. Preliminary studies will be performed to evaluate the influence of rigid immobilization, cage activity, farm activity, and vigorous daily treadmill exercise on the size and strength of normal tendons and on the strength of insertion sites into bone. We will also evaluate the influence of these exercise factors on the rate of tendon healing. Of particular importance will be studies on the exercise postoperatively after tendon repair. The purpose of this part of the study will be to determine the conditions which will maximize the quality of repair, including the proper duration of immobilization, timing onset of the exercise program and he exercise schedule. A variety of techniques will be used to evaluate the quality of repair. Correlation studies will be performed between morphologic, bioengineering and biochemical procedures. Video dimension analysis will be performed under various strain rate conditions including high speed motion picture analysis converted to the video format. It will be possible to study the repair line and the remainder of the tendon composite independently using this approach. Thi is necessary because the effects of exercise (or its deficiency) are different between various elements of the tendon composite, viz. area of repair, area of tendon proximal and distal to the repair site and the tendon insertion site. A variety of biochemical techniques will also be used to correlate with the tensile test measurements. These will include estimation of water content, total hexosamine, glycosaminoglycan, total collagen, soluble collagen, and analysis of reducible collagen cross-lilnks. The application of drugs and hormones known to modify connective tissue metabolism will be explored to determine whether the immobilization effects occurring in the early phase of repair can be overcome without impeding the tendon repair process.